Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0081—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound
  • C09C1/0084—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound containing titanium dioxide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/22—Compounds of iron
  • C09C1/24—Oxides of iron
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D17/00—Pigment pastes, e.g. for mixing in paints
  • C09D17/001—Pigment pastes, e.g. for mixing in paints in aqueous medium
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D17/00—Pigment pastes, e.g. for mixing in paints
  • C09D17/004—Pigment pastes, e.g. for mixing in paints containing an inorganic pigment
  • C09D17/007—Metal oxide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D17/00—Pigment pastes, e.g. for mixing in paints
  • C09D17/004—Pigment pastes, e.g. for mixing in paints containing an inorganic pigment
  • C09D17/007—Metal oxide
  • C09D17/008—Titanium dioxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/19—Oil-absorption capacity, e.g. DBP values
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/20—Powder free flowing behaviour
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
  • C01P2006/63—Optical properties, e.g. expressed in CIELAB-values a* (red-green axis)
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
  • C01P2006/64—Optical properties, e.g. expressed in CIELAB-values b* (yellow-blue axis)
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
  • C01P2006/65—Chroma (C*)

Definitions

• the present invention relates to the use of special iron oxide red pigments for the preparation (coloring) of aqueous titanium dioxide-containing preparations, to corresponding preparations and to a process for their preparation.
• Iron oxides are used in many technical fields. For example, they are used as color pigments in ceramics, building materials, plastics, paints, lacquers and paper, serve as a basis for various catalysts or support materials, can adsorb or absorb pollutants.
• Magnetic iron oxides find applications in magnetic storage media, toners, ferrofluids or in medical applications such as magnetic resonance imaging contrast agents.
• Iron oxides can be obtained by precipitation, hydrolysis and decomposition reactions of iron salts. By far the greatest industrial importance is the Laux, Copperas, Desill, Calzinier and Penniman-Rot processes.
• hematite can also be prepared by adding a finely divided iron oxide of the modification maghemite, Y-Fe 2 O 3 , or lepidocrocite, ⁇ -FeOOH, as a germ by a direct aqueous precipitation [US Pat. No. 5,421,878; EP0645437A; WO 2009 / 100767A].
• iron oxide red pigments are produced by dissolving and oxidizing iron metal with addition of an iron salt and an iron oxide nucleus. So is in SHEN, Qing; SUN, Fengzhi; Wujiyan Gongye 1997, (6), 5-6 (CH), Wujiyan Gongye Bianjib, (CA 128: 218378) has disclosed a method in which dilute nitric acid acts on iron at an elevated temperature.
• EP 1 106577A discloses a variant of the Penniman Red process comprising the action of dilute nitric acid on iron at elevated temperature to produce germs,
• the reaction of iron with nitric acid is a complex reaction and, depending on the experimental conditions, can either lead to a passivation of the iron and thus to a standstill of the reaction or to a dissolution of the iron with formation of dissolved iron nitrate. Both reaction paths are not desired, and the production of finely divided hematite succeeds only under limited experimental conditions.
• EP 1 106577A describes such conditions for the production of finely divided hematite.
• the iron is reacted with dilute nitric acid at temperatures between 90 and 99 ° C to react.
• WO 2013/045608 describes a process for the preparation of iron oxide red pigments, in which the reaction step of the production of the germs, ie of finely divided hematite having a particle size less than or equal to 100 nm, has been improved.
• iron or a mixture of iron and water is presented. Then, usually the hematite-seed suspension is added to at least iron, and then iron (II) nitrate solution is added to the mixture.
• the reaction usually starts after the temperature of the reaction mixture is raised to 70 to 99 ° C and after the fumigation with an oxygen-containing gas is started.
• iron oxide red pigments are required whose red content a * (measured in a mixture with white pigments - called lightening - according to CIELAB) is particularly pronounced.
• the higher the red color a * determined for the coloring the clearer the red color of the dyed medium (for example lacquer, plastic, coatings, construction material, paper).
• the requirement is made that the incorporation of the iron oxide red pigments into a dispersion paint system leads to the same color shade at all times, which should be as independent as possible from the duration of the incorporation.
• the incorporation of the iron oxide red pigment in a dispersion paint system is carried out in technical equipment, such as bead mills under the action of mechanical forces on the pigment, this grinding possibly taking hours.
• a high degree of color or quality constancy is given if the color of the iron oxide red pigment changes as little as possible during fluctuations in the incorporation time. The smaller the change in color when the training period is extended, the more stable the iron oxide red pigment is called.
• One measure of color constancy is the total color separation AEab *, which is obtained by comparing the hue of two dispersion color suds derived from the same disperse color and pigment raw materials in the same equipment at different lengths Induction periods were gained. Here it is required that the resulting total color separation AEab * is as low as possible.
• the total color difference AEab * is determined according to CIELAB based on DIN EN ISO 1664-4: 201 1-07 and DIN EN ISO 787-25: 2007 from the brightness L *, the red value * and the yellow value b * according to the following formula:
• media such as concrete, plastics, paints and varnishes
• this property both in intensive coloring of the medium as well as weaker coloring by dilution with lighter pigments such as white pigments is present and also have a high grinding stability.
• the color saturation C * (also chroma, chromaticity or chroma) is often stated. This value results directly from the values a * and b * and represents the square root of the sum of the squares of a * and b *.
• a *, b *, L *, and C * are dimensionless values. Usually, however, the dimension CIELAB units is used in this context.
• the measurement has in a so-called testing in a thixotropic long-oil alkyd resin (according to DIN EN ISO 1664-4: 201 1-07 and DIN EN ISO 787-25: 2007, in deviation a long oil alkyd resin with an oil content of 64% by weight instead of 63% by weight and another thixotropic agent is used. Details are given in the Examples and Methods section) have been found to be particularly meaningful. This test is called according to the invention as Lackabtestung.
• the alkyd resin has the advantage that it does not dry. So measurements are faster possible, as if the paste must first be dried before the measurement. Further details on this test method are given in the Examples and Methods section.
• the pigment is dispersed in a clear paste under standard conditions defined in the standard.
• the color values of the pigmented color paste are then determined.
• the paste is added to the paste titanium dioxide in the modification rutile, so that a ratio of pigment to titanium dioxide of 1: 5 is achieved.
• the lightening can still evaluate the evaluation of the color strength and color purity of a pigment with the presence of a white pigment that lightens the color.
• iron oxide red pigments with an a * value in the peak of 29 to 30.5 CIELAB units can be prepared by the Copperas, precipitation and Penniman red process. These are distinguished in the Purton in one of the Lackabtestung by the special red and yellow cast and the color saturation C * is up to 40.0 CIELAB units.
• the color saturation C * is up to 40.0 CIELAB units.
• the lightening ie in the above-described mixture with titanium dioxide, however, they show a significant decrease in the red sting, ie lower a * values. From an application point of view, however, it would be particularly advantageous to have available iron oxide red pigments which have a very high red tinge both in the pur tone and in the lightening as a mixture with titanium dioxide.
• the invention relates to the use of a hematite pigment whose sum of the a * values in the shade and in the lightening in the paint application of 58.0 to 61, 0 CIELAB units, preferably from 58.0 to 60.0 CIELAB units, further preferably from 58.5 to 61, 0 CIELAB units, further preferably from 58.5 to 60.0 CIELAB units, more preferably from 59.0 to 61, 0 CIELAB units, more preferably from 59.0 to 60.0 for the preparation of an aqueous, titanium dioxide-containing preparation.
• A) hematite pigment whose sum of the a * values in the shade and in the lightening in the paint application of 58.0 to 61, 0 CIELAB units, preferably from 58.0 to 60.0 CIELAB units, further preferably from 58.5 to 61, 0 CIELAB units, further preferably from 58.5 to 60.0 CIELAB units, more preferably from 59.0 to 61, 0 CIELAB units, more preferably
• the pigments according to the invention whose sum of the a * values in the shade and in the lightening in the paint test from 58.0 to 61.0 CIELAB units, preferably from 58.0 to 60.0 CIELAB units, further preferred from 58.5 to 61, 0 CIELAB units, further preferably from 58.5 to 60.0 CIELAB units, more preferably from 59.0 to 61, 0 CIELAB units, further particularly preferably from 59.0 to 60.0 CIELAB units and an organic coating, preferably with oils, waxes, fatty acids or fatty acid salts, and / or an inorganic coating, preferably with inorganic salts such as carbonates, oxides or hydroxides of alkali and alkaline earth metals or of Mg, Zn, Al, La, Y , Zr, Sn and / or Ca or not.
• the preferred hematite pigments have the modification a-Fe 2 0 3 . In a further preferred embodiment, they comprise a particle size of 0, 1 to 0.3 ⁇ . More preferably, at least 80 wt.% Of the preferred hematite pigments have a particle size of 0, 1 to 0.3 ⁇ on.
• the hematite pigments have an oil number of 15 to 26, preferably from 15 to 24, measured according to DIN EN ISO 787-5: 1995, on.
• the hematite pigments have a water content of 1, 0 wt.% Or more, preferably from 1, 0 to 5.0 wt.% To.
• the water is particularly preferably present as water of crystallization.
• hematite pigments preferably have a chloride content of 0.001 to 0.1% by weight of chloride.
• chloride content is meant according to the invention the total content of chloride in the hematite pigment.
• hematite pigments which have the modification a-Fe 2 0 3 , a particle size of 0, 1 to 0.3 ⁇ , most preferably at least 80 wt.% Of hematite pigments have a particle size of 0, 1 bis 0.3 ⁇ possess and an oil number of 17 to 26, preferably from 19 to 24, measured according to DIN EN ISO 787-5: 1995 and preferably have a water content of 1, 0 wt.% Or more, preferably from 1, 0 to 5.0% by weight. Production of hematite pigments
• the hematite pigments are preferably prepared by reacting iron with an aqueous hematite-seed suspension and an iron (II) salt solution, preferably iron (II) nitrate solution, in the presence of at least one oxygen-containing gas, the so-called Penniman-Red method ,
• the hematite pigments are prepared by a process which precludes a calcination step at temperatures greater than 600 ° C.
• the production process comprises at least the reaction of iron, hematite-seed suspension containing hematite nuclei having a particle size of 100 nm or less and a BET specific surface area of from 40 m 2 / g to 150 m 2 / g (measured according to DIN 66131), and iron (II) nitrate solution in the presence of at least one oxygen-containing gas at temperatures of 70 to 99 ° C, characterized in that the reaction during gassing with an oxygen-containing gas in a pH range of pH 2, 2 to pH 4.0, preferably from pH 2.2 to pH 3.0, producing a hematite pigment suspension.
• the reaction takes place at least in the first 40 hours during the fumigation with an oxygen-containing gas, preferably for more than 80% of the first 40 hours during the fumigation in a pH range of pH 2.2 to pH 4.0, preferably from pH 2.2 to pH 3.0.
• the pH of the reaction suspension by additionally introducing gaseous nitrogen into the reaction mixture, preferably into the liquid phase, in addition to the oxygen-containing gas.
• gaseous nitrogen preferably contains from 0 to 10% by volume of oxygen, preferably from 0 to 1% by volume of oxygen.
• the oxygen-containing gas contains from 15 to 100% by volume of oxygen.
• so much gaseous nitrogen is introduced into the reaction mixture that the oxygen content, based on the total volume of oxygen-containing gas and gaseous nitrogen, is from 0 to 15% by volume, preferably from 0 to 10% by volume.
• the introduction of the gaseous nitrogen can be such that the introduction of the oxygen-containing gas is either continued or interrupted, but the sum of the gassing volumes with oxygen-containing gas and gaseous nitrogen is at least 1 m 3 gas volume / m 3 batch volume / hour.
• the pH of the reaction mixture increases so rapidly that the pH of the reaction mixture is within the limit of pH 2.2 to pH 4.0, preferably from pH 2.2 to pH 3.0 can be kept.
• the Nitrogen introduction is again terminated after reaching the upper pH limit of more than pH 4.0, preferably more than pH 3.0, and only after reaching the lower pH limit less than pH 2.2, started again.
• FIG. 1 shows a pH profile of such a process. The reaction time is shown on the x-axis and the pH of the reaction mixture is shown on the y-axis.
• the pH of the reaction mixture is shown on the x-axis.
• the pH of the reaction mixture is 2.5 or more, and is defined by the mixture of the acidic ferrous nitrate solution and the acidic hematite-seed suspension.
• the pH decreases within about 20 hours to below 2, 1 and then increases within another 40 hours back to a pH of 2, 1 to 2,3.
• hematite pigments are obtained which have a sum of the a * values in the pur tone and in the lightening of 57.5 and less.
• the reaction is carried out until the hematite pigment reaches the desired hue in the paint application, i. has the corresponding a * values in the purton and in the lightening.
• the a * values increase during the reaction in the presence of at least one oxygen-containing gas at temperatures of from 70 to 99.degree. Therefore, samples are taken during the reaction at different times and examined in the Lackabtestung.
• a paint inspection test can be performed within one hour. Within this time, hematite color values in the reaction mixture may change slightly again.
• the skilled person will be able to determine the optimum time for terminating the reaction.
• the preferred method comprises separating the hematite pigment from the hematite pigment suspension by conventional methods.
• the reaction of iron, hematite-seed suspension and iron (II) nitrate solution in the presence of at least one oxygen-containing gas at temperatures of 70 to 99 ° C is also called pigment buildup.
• the hematite pigments prepared according to the invention have the hematite (a-Fe 2 0 3 ) modification and are therefore also called hematite pigments in connection with this invention.
• the pigment structure according to such a method is carried out in one embodiment in a reactor according to FIG.
• FIG. 3 shows the representation of a device which is preferably used.
• NOX nitrogen oxide-containing material stream (waste gas from the production of the hematite pigment suspension)
• Reactor 1 typically comprises one or more reaction vessels of materials resistant to the feedstocks.
• Simple reaction vessels may e.g. brick or tiled container embedded in the ground.
• the reactors also include, for example, containers made of glass, nitric acid-resistant plastics, such as e.g. Polytetrafluoroethylene (PTFE), steel, e.g. Enamelled steel, plastic or lacquer-coated steel, stainless steel with the material number 1.44.01.
• the reaction vessels may be open or closed. In preferred embodiments, the reaction vessels are closed.
• the reaction vessels are typically designed for temperatures between 0 and 150 ° C and for pressures of 0.05 MPa to 1, 5 MPa.
• FIG. 1 A preferred embodiment of a reactor 1 is shown in FIG.
• Reactor 1 comprises at least reaction vessel 11, template 12 for iron, gassing unit 13 for the at least one oxygen-containing gas A, inlet 111 for at least iron (II) nitrate solution and hematite-seed suspension, outlet 112 for a nitrogen oxide-containing material flow NOX, outlet 113 for the Hematite pigment suspension, liquid phase outlet 114, liquid phase inlet 115, an agitator 2 comprising a drive 21, a connection between drive and stirrer 22, a stirrer 23, a pump 31 and a pH electrode 41.
• Outlet 114, inlet 115 and pump 31 are connected to each other via a line, that the liquid phase can be promoted in the circulation out of the reaction vessel 11 out and back into the reaction vessel 11 into it.
• a further preferred embodiment of a reactor 1 has at least reaction vessel 11, template 12 for iron, gassing unit 13 for the at least one oxygen-containing gas A, inlet 111 for at least iron (II) nitrate solution and hematite-seed suspension, outlet 112 for a nitrogen oxide-containing material stream NOX and outlet 113 for the hematite pigment suspension and optionally a pH electrode 41.
• a further preferred embodiment of a reactor 1 has at least reaction vessel 11, template 12 for iron, gassing unit 13 for the at least one oxygen-containing gas A, inlet 111 for at least iron (II) nitrate solution and hematite-seed suspension, outlet 112 for a nitrogen oxide-containing material stream NOX , Outlet 113 for the hematite pigment suspension, a stirring device 2 comprising a drive 21, a connection between the drive and stirrer 22, a stirring member 23 and optionally a pH electrode 41 on.
• a further preferred embodiment of a reactor 1 has at least reaction vessel 11, template 12 for iron, gassing unit 13 for the at least one oxygen-containing gas A, inlet 111 for at least iron (II) nitrate solution and hematite-seed suspension, outlet 112 for a nitrogen oxide-containing material stream NOX Hematite pigment suspension outlet 113, liquid phase outlet 114, liquid phase inlet 115, pump 31 and, optionally, pH electrode 41.
• Figure 1 pH profile of an implementation of the preferred method.
• the time (h) is plotted on the x-axis, the pH of the reaction mixture on the y-axis.
• FIG. 2 pH profile of a nitrate process according to the prior art. The time (h) is plotted on the x-axis, the pH of the reaction mixture on the y-axis.
• FIG. 3 Reactor 1 for carrying out the preferred method
• FIG. 4 Stirring device 2
• aqueous hematite-seed suspensions used in the preferred method and the hematite nuclei contained therein are known from the prior art. Reference is made to the description of the prior art.
• the hematite nuclei contained in the aqueous hematite-germ suspension include those having a particle size of 100 nm or less and a BET specific surface area of 40 m 2 / g to 150 m 2 / g (measured according to DIN 66131).
• the particle size criterion is satisfied when at least 90% of the hematite nuclei have a particle size of 100 nm or less, more preferably from 30 nm to 90 nm.
• the aqueous hematite seed suspensions used in the preferred method typically comprise hematite nuclei having a round, oval or hexagonal particle shape.
• the finely divided hematite typically has a high purity.
• Manganese, chromium, aluminum, copper, nickel, cobalt, and / or titanium are contained in various concentrations as foreign metals in the iron scrap used for the production of the hematite-seed suspension, which also precipitate in the reaction with nitric acid to oxides or oxyhydroxides and can be incorporated into the finely divided hematite.
• those contained in the hydrous hematite-germ suspension Hematite nuclei have a manganese content of from 0.1 to 0.7% by weight, preferably from 0.4 to 0.6% by weight. With germs of this quality, strong red iron oxide pigments can be produced.
• the iron (II) nitrate solutions used in the preferred process are known from the prior art. Reference is made to the description of the prior art. Typically, these iron (II) nitrate solutions have concentrations of 50 to 150 g / l Fe (NO 3 ) 2 (stated Fe (N0 3 ) 2 based on anhydrous substance). In addition to Fe (N0 3 ) 2 , the iron (II) nitrate solutions may also contain amounts of 0 to 50 g / l Fe (N0 3 ) 3 . However, the lowest possible amounts of Fe (N0 3 ) 3 are advantageous.
• iron in the preferred method usually iron in the form of wire, sheets, nails, granules or coarse chips is used.
• the individual parts are of any shape and usually have a thickness (for example, measured as the diameter of a wire or as the thickness of a sheet) of approximately 0.1 millimeter to approximately 10 millimeters.
• the size of wire bundles or sheets used in the process is usually measured by practical considerations.
• the reactor must be able to be filled with this feed without difficulty, which usually takes place through a manhole.
• Such iron is produced inter alia as scrap or as a by-product in the metalworking industry, for example stamped sheets.
• the iron used in the preferred process generally has an iron content of> 90% by weight.
• impurities in this iron usually foreign metals such as manganese, chromium, silicon, nickel, copper, and other elements occur. However, it can also be used without disadvantages iron with a higher degree of purity.
• iron is used in an amount between 20 and 150 g / l based on the volume of the reaction mixture at the beginning of the preferred reaction.
• the iron preferably in the form of stamped sheets or wires, on the iron template over the area with a preferred bulk density of less than 2000 kg / m 3 , more preferably less than 1000 kg / m 3 distributed.
• the bulk density can be achieved, for example, by bending sheets of at least one iron grade and / or by deliberately laying the iron. As a result, typically more than 90 volume percent of the oxygen-containing gas injected under the iron master passes through the iron master without the oxygen-containing gas accumulating under the iron master.
• the iron template allows an exchange of suspension and gas through existing in the iron template openings.
• Typical embodiments for the iron template may be sieve trays, perforated trays or grids.
• the ratio between the cumulative area at openings and the total template area is from 0.1 to 0.9, preferably from 0.1 to 0.3.
• the holes or openings required for the suspension exchange are typically chosen so that falling through of the iron by the iron template is largely avoided.
• a wall is preferably attached laterally to the iron template device, which avoids falling of iron. This wall may be permeable to, for example, executed as a grid, or suspension-impermeable and, for example, the shape of a tube or an open-top parallelepiped.
• the amount of iron reacted in the reaction is determined by differential weighing of the amount of iron before and after the reaction.
• a certain amount of iron is introduced and then further iron is added in portions during the entire reaction time, a total of a significant excess, typically 150 to 200% by weight of the amount of iron reacted in the reaction being used. Although this may raise the pH of the reaction mixture, an improvement in the color properties of the resulting pigments can not be achieved.
• low-salt water is used as the water in the process for producing the hematite-seed suspension and / or the iron (II) nitrate solution and / or the hematite pigment suspension.
• the conductivity can be simplified.
• Low-salt water in the sense of the invention has a conductivity of 20 ⁇ 3 / ⁇ or less, preferably of 10 ⁇ 3 / ⁇ or less, particularly preferably of 5 ⁇ 3 / ⁇ or less.
• Polyvalent anions e.g.
• Phosphate, silicate, sulfate and carbonate which are often present in process water, can have a flocculating effect on the iron oxide pigments and cause the iron oxide pigment to flocculate during the reaction and settle on the bottom of the reactor as sediment.
• low salt water e.g. demineralized water (demineralised water), distilled water or reverse osmosis water.
• the color values of the hematite pigments are used.
• low-salt water is used as the water in the process for producing the hematite-seed suspension and the iron (II) nitrate solution and the hematite pigment suspension. This will once again improve the color values of the pigments.
• the at least one oxygen-containing gas is preferably selected from air, oxygen, air heated above ambient temperature or water enriched with water vapor.
• the reaction of at least iron, hematite-seed suspension and iron (II) nitrate solution takes place in such a way that at least the liquid phase present during the reaction is mixed by means of mechanical and / or hydraulic mixing or not. If there is suspended hematite in the liquid phase, the mechanical and / or hydraulic mixing is preferably carried out in such a way that the hematite suspended in the liquid phase remains evenly distributed in the liquid phase and does not accumulate in the lower part of the liquid phase.
• the liquid phase By mechanical mixing is meant the mixing of the liquid phase by means of suitable devices.
• the liquid phase also contains solids suspended therein, such as the hematite nuclei or the hematite pigment, as well as other solids, e.g. Iron particles.
• the suitable devices comprise stirring devices, for example axial stirrers, radial stirrers and tangential stirrers.
• Stirring devices such as stirring device 2 in FIG. 1, have at least one stirring element, such as stirring element 23 in FIG. 1, for example propellers, spirals or blades, which generate a flow of the liquid phase.
• Stirrers also typically have a drive, such as drive 21 in Figure 1, e.g.
• stirrer e.g. a motor, and a connection between stirrer and drive 22, e.g. a wave or a magnetic coupling on.
• a connection between stirrer and drive 22 e.g. a wave or a magnetic coupling on.
• blade stirrers preferably generate radial flows, inclined blade stirrers and propeller stirrers axial flows. Axial flows may be directed upwards or downwards.
• a mechanical mixing of the liquid phase is preferred, which is directed axially from bottom to top on the iron.
• the at least one stirring element is preferably located below and / or above the iron.
• the stirrer are axial stirrers, more preferably inclined blade stirrers or propeller stirrers.
• flow baffles are additionally present on the inside of the wall of the reaction container 1. As a result, co-rotation of the liquid phase and the formation of trumps occurring thereby is avoided.
• the degree of mechanical mixing is defined by the outer peripheral speed of the stirring element, for example the stirring element 23.
• Preferred peripheral speeds are 0.5 - 15 m / s, measured on the circumference of the circle formed by the diameter of the stirring element.
• the power input into the liquid phase which can be derived from the power consumption of the stirrer, is preferably 0.1 to 5 kW per m 3 batch volume, preferably 0.4 to 3 kW per m 3 batch volume.
• the ratio of agitator ore diameter to internal reactor diameter is preferably 0.1 to 0.9.
• Of the Power input into the liquid phase is calculated from the power consumption of the stirrer multiplied by the efficiency of the stirrer in percent. Typical efficiencies of stirrers used in the preferred process are between 70 and 90%.
• peripheral speeds of 1 to 15 m / s and a power input of at least 0.4 kW / m 3 batch volume are particularly preferred.
• hydraulic mixing takes place with the aid of a pump, for example pump 31, which removes the liquid phase from the reactor at an outlet, for example outlet 114, and supplies it to another location at an inlet, for example inlet 115. Flows are generated at the inlet and outlet as well as in the entire reaction mixture. Hydraulic mixing takes place by means of a pump, for example pump 31, which removes the liquid phase from the reactor at an outlet, for example outlet 114, and supplies it to the reactor at another location at an inlet, for example inlet 115. Flows are generated at the inlet and outlet as well as in the entire reaction mixture.
• pumping amounts of 0.1 to 20 batch volumes / hour are preferred.
• the circulation rate is 30 m 3 batch volume and a value of 5 approach volumes / hour 150 m 3 / hour.
• recirculation quantities are preferred which produce a flow velocity at the inlet, for example inlet 115, of at least 0.05 m / s, preferably of at least 0.06 to 15 m / s.
• the flow velocities at the input are measured directly at the transition of the line from which the recirculated liquid phase flows into the reaction mixture in the interior of the reactor.
• the flow from the inlet is directed to the iron master, for example iron master 12, preferably from below the iron master onto the iron master at a distance of less than 2 m, preferably less than 1 m.
• the inlet for example inlet 115, is designed as a pipeline or as a two-substance radiator or as a nozzle.
• the reaction of at least iron, hematite-seed suspension and iron (II) nitrate solution takes place in such a way that it is gassed with at least one oxygen-containing gas having a gassing volume of 6 m 3 gas volume / m 3 batch volume / hour or less, preferably from 0.2 to 6 m 3 gas volume / m 3 batch volume / hour, more preferably from 0.2 to 5 m 3 gas volume / m 3 batch volume / hour, very particularly preferably from 0.2 to 3 m 3 gas volume / m 3 batch volume / hour.
• the gassing is carried out with at least one oxygen-containing gas without mechanical and without hydraulic mixing. Only the gassing with oxygen-containing gas here leads to a strong mixing of the reaction mixture, for example at Begasungsvolumina 7-10 m 3 per hour and per m 3 Batch volume, whereby in the reaction mixture, a strong convection and a strong bubbling, similar to a strong boiling of a liquid, is produced on the surface of the reaction mixture.
• the reaction mixture preferably comprises all starting materials and the resulting solid, liquid and gaseous products.
• a nitric oxide-containing stream NOX is formed.
• the nitrogen oxide-containing material stream NOX is passed out of the reactor, for example via the outlet 112 of reactor 1.
• the batch volume is preferably defined as the total volume of the liquid and solid constituents of the reaction mixture that are at a particular time of reaction in the reaction vessel , for example in reactor 1.
• the batch volume can be determined, for example, at any time during the reaction via a fill level indicator of the reactor in which the reaction is carried out.
• the gassing with at least one oxygen-containing gas is preferably carried out such that the at least one oxygen-containing gas below the iron template, for example template 12, is introduced into the liquid phase of the reaction mixture.
• a gassing unit for example gassing unit 13, such as e.g. Gassing ring, nozzles, (two) -Stoffstrahlern or a perforated pipe, which is located within the reaction mixture used.
• the at least one oxygen-containing gas must have sufficient pressure to be able to act against the hydrostatic pressure of the liquid column of the reaction mixture.
• gaseous nitrogen is then introduced into the reaction mixture when the pH of the reaction mixture falls below 2.2.
• the introduction of gaseous nitrogen into the reaction mixture is terminated when the pH is again in the range of pH 2.2 to pH 4.0, preferably from pH 2.2 to pH 3.0.
• the pH of the reaction mixture can take place via regular sampling of the reaction mixture or via a pH measuring probe located inside the reaction container, for example pH probe 41.
• the pH probe 41 is attached so that it is completely within the reaction mixture.
• the pigment is built up on the hematite seed contained in the liquid phase, thereby producing a hematite pigment suspension whose color values, preferably its a * and b * values in the paint process, throughout the reaction change in pigment buildup changing particle size and / or morphology.
• the time at which the preferred method is discontinued is determined. The preferred method is discontinued if the hematite pigment in the paint application is particularly preferred for the required sum of the a * values in the pur tone and in the brightening in the paint finish of at least 58.0 CIELAB units, preferably more than 58.5 CIELAB units has more than 59.0 CIELAB units.
• the separation of the hematite pigment from the hematite suspension is carried out by customary methods, preferably by filtration and / or sedimentation and / or centrifugation. Likewise preferably washing takes place after separation of the filter cake and subsequent drying of the filter cake. Likewise preferably, one or more sieving steps, particularly preferably with different mesh sizes and with descending mesh sizes, are carried out before the hematite pigment is separated from the hematite pigment suspension. This has the advantage that thereby foreign bodies, for example metal pieces, are separated from the hematite pigment suspension, which would otherwise contaminate the hematite pigment.
• sulfate salt for example iron (II) sulfate and / or an alkali metal or alkaline earth metal sulfate, preferably iron (II) sulfate and / or sodium sulfate, to the hematite pigment suspension during or before sieving and / or during or before separation.
• the hematite pigment thus separated is dried, for example with filter driers, belt driers, kneading driers, spinflash dryers, drying cabinets or spray driers.
• the drying is carried out with belt dryers, plate dryers, Knettrocknern and / or spray dryers.
• the preferred process provides hematite pigments which are particularly suitable for the use according to the invention for the production of aqueous, titanium dioxide-containing, stable-to-stable pigment preparations.
• titanium dioxide of the rutile type is used, in particular one with an average particle size of 0.25 to 0.35 ⁇ , preferably from 0.30 to 0.31 ⁇ .
• Preferred titanium dioxide likewise has an oil adsorption of 18 to 24 g / 100 g measured according to DIN EN ISO 787-5: 1995.
• the titanium dioxide has a surface coating comprising aluminum oxide (Al 2 O 3 ) and silicon oxide (SiO 2).
• the titanium oxide is preferably used in an amount of 5 to 20% by weight, in particular 8 to 15% by weight, based on the aqueous preparation. Preference is furthermore given to a weight ratio of hematite pigment to TiO 2 of from 1: 0.5 to 1:20, in particular from 1: 1 to 1:10.
• the aqueous pigment preparation to be prepared preferably comprises a binder, preferably binder, dispersions of plastic polymers or copolymers, monomers most commonly used being acrylic acid, acrylic acid esters, acrylic anhydride, acrylonitrile, methacrylic acid, maleic acid, maleic acid esters, maleic anhydride, styrene, olefins, vinyl chloride or vinyl acetate.
• a binder preferably binder, dispersions of plastic polymers or copolymers, monomers most commonly used being acrylic acid, acrylic acid esters, acrylic anhydride, acrylonitrile, methacrylic acid, maleic acid, maleic acid esters, maleic anhydride, styrene, olefins, vinyl chloride or vinyl acetate.
• aqueous pigment preparations may comprise wetting and dispersing agents and water and, if appropriate, auxiliaries customary for pigment preparations, for example additional solvents, humectants, preservatives, defoamers, pH regulators and rheology additives which serve as antisettling agents.
• auxiliaries customary for pigment preparations for example additional solvents, humectants, preservatives, defoamers, pH regulators and rheology additives which serve as antisettling agents.
• the wetting and dispersing agents for inorganic pigments have the task of wetting the pigments, dispersing them and stabilizing the pigment preparations.
• the prior art preferably uses polymeric dispersants and anionic, cationic and nonionic surfactants in order to disperse the pigments in aqueous dispersions or to modify the surface.
• polymeric dispersants usually low molecular weight polymers of acrylic acid or copolymers of acrylic acid, methacrylic acid and maleic acid and their sodium, potassium or ammonium salts are used.
• the anionic surfactants used are amphiphilic compounds whose hydrophobic group is an aliphatic or aromatic radical and whose hydrophilic group contains a carboxylic, sulfonic or phosphonic acid group or represents an ester of sulfuric acid or phosphoric acid.
• Preferred nonionic surfactants which are used as dispersants for pigment preparations are fatty alcohol ethoxylates, alkylphenol ethoxylates and copolymers of ethylene oxide, propylene oxide and styrene oxide.
• Suitable anionic dispersants are preferably anionic surfactants from the group of the sodium, potassium and ammonium salts of fatty acids, alkylbenzenesulfonates, alkylsulfonates, olefinsulfonates, polynaphthalenesulfonates, alkyl sulfates,
• Suitable humectants and solvents are preferably glycol ethers, which are understood here to mean, in particular, compounds having ethoxy and / or propoxy groups which have average molar masses of from 200 to 20,000 g / mol, in particular polyethylene glycol ethers or polypropylene glycol ethers having an average molar mass of from 200 to 20,000 g / mono-, di- or triethylene glycol, mono-, di- or tripropylene glycol, methyl, ethyl, propyl, butyl or higher alkylpolyalkylene glycol ethers having 1, 2, 3 or more ethylene glycol or propylene glycol units such as, for example, methoxypropanol, dipropylene glycol mono methyl ether, tripropylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, butyl polyethylene glycol ether, propyl polyethylene glycol ether, ethy
• auxiliaries of the aqueous pigment preparations according to the invention are preferably water-soluble organic or hydrotropic substances which optionally also serve as solvents.
• Particularly suitable are, for example, formamide, urea, tetramethylurea, ⁇ -caprolactam, glycerol, diglycerol, polyglycerol, N-methylpyrrolidone, 1, 3-diethyl-2-imidazolidinone, thiodiglycol, sodium benzenesulfonate, sodium xylenesulfonate, sodium toluenesulfonate, sodium Cumene sulfonate, sodium dodecyl sulfonate, sodium benzoate, sodium salicylate, sodium butyl monoglycol sulfate.
• Suitable defoamers are preferably mineral oil defoamers and their emulsions, silicone oil defoamers and silicone oil emulsions, polyalkylene glycols, polyalkylene glycol fatty acid esters, fatty acids, higher alcohols, phosphoric acid esters, hydrophobically modified silica, aluminum tristearate, polyethylene waxes and amide waxes.
• Suitable rheology additives as viscosity modifiers are e.g. Starch and cellulose derivatives and hydrophobically modified ethoxylated urethanes (HEUR) thickeners, alkali-swellable acrylate thickeners, hydrophobically modified acrylate thickeners, polymers of acrylamidomethylpropanesulfonic acid, benthonite thickeners or fumed silica. Pot preservatives are added to stabilize the aqueous pigment preparations and to prevent the uncontrolled proliferation of bacteria, algae and fungi.
• HEUR hydrophobically modified ethoxylated urethanes
• Suitable biocides are formaldehyde, formaldehyde-releasing components, methylisothiazolinone, chloromethylisothiazolinone, benzisothiazolinone, bronopol and dibromodicyanonobutane.
• organic or inorganic bases and acids are used as buffer substances and pH regulators.
• Preferred organic bases are amines, such as. For example, ethanolamine, diethanolamine, triethanolamine, ⁇ , ⁇ -dimethylethanolamine, diisopropylamine, 2-amino-2-methyl-1-propanol or dimethylaminomethylpropanol.
• Preferred inorganic bases are sodium, potassium, lithium hydroxide or ammonia.
• the invention also relates to a pigment preparation comprising at least A) a hematite pigment as described above,
• Preferred pigment preparation of the invention comprise:
• the hematite pigments additionally have a Newtonian flow behavior when they are in the form of pastes, for example in the form of pigment universal pastes.
• the Newtonian flow behavior is defined by a certain dependence of the viscosity of the paste on the shear rate.
• the viscosity is defined as a measure of the viscosity of a fluid, for example a pigment paste, and has the unit Pa » s. The lower the viscosity, the thinner the fluid.
• the shear rate is a term from rheology, ie the theory of deformation and flow behavior of material and is defined as a measure of the mechanical stress, which is subjected to a sample in a rheological measurement. Shear velocity is also called shear rate.
• the shear rate has the unit of inverse time, usually 1 / s.
• their viscosity is independent of the shear rate at which the viscosity is measured.
• the viscosity for pigment pastes is measured according to the invention using a plate-and-cone viscometer (Rheo3000 from Brookfield Engineering Laboratories, Inc., USA) at shear rates of 500 / s to 2000 / s.
• the criterion of a Newtonian flow behavior is met according to the invention when the viscosity at each measurement at shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s by 10% or less, preferably by 5% or less, of deviates from the arithmetic mean of the measured values of shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s. If a measurement is at a shear rate, for example, if the viscosity is greater than that of the maximum measurable viscosity, then the criterion of a Newtonian flow behavior according to the invention is likewise not fulfilled.
• the measurement of the viscosity at different shear rates is carried out according to the invention at 20 ° C.
• the pigment paste used for the measurement is a customary universal paste with the following composition in% by weight:
• PEG 200 Polyethylene glycol 200, Merck KGaA, Germany
• Byk 044 Silicone defoamer for aqueous printing inks and overprint varnishes. BYK Chemie GmbH, Germany
• Disperbyk 102 Solvent-free wetting and dispersing additive from BYK Chemie GmbH, Germany
• Disperbyk 185 Solvent-free wetting and dispersing additive from BYK Chemie GmbH, Germany
• the paste is prepared by mixing all components together for 30 minutes in a dissolver at 4500 rpm.
• This test is called paste viscosity test.
• the iron oxide red pigments used according to the invention have a sum of the a * values in the shade and in the lightening in the paint finish of at least 58.0 CIELAB units, preferably more than 58.5 CIELAB units, particularly preferably more than 59 , 0 CIELAB units, and in the paste viscosity test, a Newtonian flow behavior, wherein the viscosity at each measurement at shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s by 10% or less, preferably by 5% or less deviates from the arithmetic mean of the shear rate readings of 500 / s, 1000 / s, 1500 / s, and 2000 / s.
• the iron oxide red pigments used according to the invention have a sum of the a * values in the Purton and in the lightening in the paint test from 58.0 to 61.0 CIELAB units, preferably from 58.0 to 60.0 CIELAB Units, further preferably from 58.5 to 61, 0 CIELAB units, further preferably from 58.5 to 60.0 CIELAB units, more preferably from 59.0 to 61, 0 CIELAB units, more preferably from 59.0 to 60 , 0, and in the paste viscosity test a Newtonian flow behavior, wherein the viscosity at each measurement at shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s by 10% or less, preferably by 5% or less, of the arithmetic mean of the measured values of the shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s.
• the pigments used according to the invention have a sum of the a * values in the shade and in the lightening in the paint finish of at least 58.0 CIELAB units, preferably more than 58.5 CIELAB units, particularly preferably more than 59.0 CIELAB units, and in the paste viscosity test, viscosities at shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s from 0.300 to 0.400 Pa-s.
• the pigments used according to the invention have a sum of the a * values in the shade and in the lightening in the paint finish of 58.0 to 61.0 CIELAB units, preferably from 58.0 to 60.0 CIELAB units, further preferably from 58.5 to 61, 0 CIELAB units, further preferably from 58.5 to 60.0 CIELAB units, more preferably from 59.0 to 61, 0 CIELAB units, further particularly preferably from 59.0 to 60.0 , particularly preferably more than 59.0 CIELAB units, and in the paste viscosity test viscosities at shear rates of 500 / s, 1000 / s, 1500 / s and 2000 / s from 0.300 to 0.400 Pa-s on.
• the hematite pigments used according to the invention have a Newtonian flow behavior in the form of pigment pastes. This simplifies the processability of the pigments in the production of pastes and paints.
• the hematite pigments used according to the invention can be prepared by a simpler method than, for example, the Copperas pigments.
• the invention also relates to a process for the preparation of the aqueous pigment preparation according to the invention, characterized in that at least
• Water used for preparing the aqueous pigment preparations according to the invention is preferably used in the form of distilled or demineralized water. Also drinking water (tap water) and / or water of natural origin can be used. Water is preferably present in the aqueous pigment preparation according to the invention at from 10 to 65% by weight.
• the aqueous pigment preparations according to the invention preferably have a viscosity of 10 to 10,000 mPas, preferably 50 to 5,000 mPas and particularly preferably 300 to 3,000 mPas, measured with a cone-and-plate viscometer at a shear rate of 1/60 sec z. As a Haake Viscometer 550 Fa. Thermo Haake.
• the present invention also provides a process for the preparation of the pigment preparations according to the invention by dispersing the component (A) in the form of powder or granules in the presence of water and the other components in a conventional manner, then optionally admixing further water and the preserving aqueous pigment dispersion with water to the desired concentration.
• agitators For dispersion, agitators, dissolvers (sawtooth stirrers), rotor-stator mills, ball mills, stirred ball mills such as sand and pearl mills, high-speed mixers, kneaders, roller mills or high performance bead mills can be used.
• the fine dispersion or milling of the pigments is carried out to the desired fineness of milling and can be carried out at temperatures in the range of 0 to 100 ° C, advantageously at a temperature between 10 and 70 ° C, preferably at 20 to 60 ° C.
• the pigment preparation can be further diluted with water, preferably deionized or distilled water.
• iron oxide red pigments are obtained, which differ from conventional, well-known iron oxide red pigments due to high color purity and, at the same time, high grinding stability. Examples and methods:
• the content of iron (II) nitrate can be determined indirectly via the measurement of the iron (II) content via a potentiometric titration of a hydrochloric acid acidified sample solution with cerium (III) sulfate. pH measurement:
• pH measurements were performed with a Knick, Protos MS3400-160 measuring instrument using Knick, MemoSens, SE533X / 2-NMSN. Before the measurement, a calibration was carried out with buffer solutions of pH 4.65 and pH 9.23 (according to DIN 19267). The pH was measured within the stirred reaction vessel at 85 ° C.
• the determination of the chloride content is carried out by ion chromatography.
• Iron blanking sheets 0.8 mm thick were used which had a manganese content of less than 2500 ppm manganese, less than 150 mg chromium, less than 0.07% carbon, less than or equal to 500 ppm aluminum, less than or equal to 400 ppm titanium equal to 250 ppm of copper.
• the low-salt water used (demineralised water) has a conductivity of 4 ⁇ 3 / ⁇ .
• the ion concentration can be deduced via the conductivity value.
• the measurement was carried out via an electrochemical resistance measurement with a device from WTW.
• demineralized water eg distilled water or purified water from a reverse osmosis system can be used, as long as the conductivity meets the above specification.
• the test paste clear (thixotropic long-oil alkyd resin produced in accordance with DIN EN ISO 787-25: 2007) contains 95% by weight alkyd resin (WorleeKyd P151 from Worlee-Chemie GmbH, Germany) and as thixotropic agent 5% by weight Luvotix HAT (Lehmann & Voss & Co. KG, Germany).
• the Luvotix is stirred into the preheated to 70 to 75 ° C alkyd resin and then stirred at 95 ° C until all the thixotropic agent has dissolved.
• the cooled paste is finally rolled bubble-free on a three-roll mill.
• test paste clear 5.00 g of the test paste clear are applied to the lower part of the plate dyeing machine (TFAM). 2.6 g of the pigment to be tested becomes clear with the "test paste" on the lower plate of the paint-dresser out of the center with the palette knife without Pre-mixed pressure until completely wetted. Subsequently, this mixture is dispersed with 3 x 25 turns. After every 25 revolutions, the material to be ground is removed from the upper plate with the palette knife and mixed again with the material to be ground on the lower plate and distributed outside the center. The Farbausreibmaschine is charged during the entire dispersion on the front bracket with 2.5 kg additional weight. The prepared paste is mixed with the palette knife and transferred to a paste plate until it is measured. For the measurement, the excess paste on the pasty plate is removed by means of a paste knife with slight pressure. After a rest period of 1 minute, the color values are measured immediately.
• TFAM plate dyeing machine
• the respective pigment is premixed with the binder on the bottom plate of the paint stripping machine outside the center with the palette knife without pressure until it is completely wetted. Subsequently, this mixture is dispersed with 5 x 25 turns. After every 25 revolutions, the material to be ground is removed from the upper plate with the palette knife while the motor is running and mixed again with the material to be ground on the lower plate and distributed outside the center point. The Farbausreibmaschine is charged during the entire dispersion on the front bracket with 2.5 kg additional weight. The prepared paste is mixed with the palette knife and transferred to a paste plate until it is measured.
• the excess paste on the pasty plate is removed by means of a paste knife with slight pressure. After a rest period of 1 minute, the color values are measured immediately.
• dispersing aggregates such as. B. Microdismembrator S (Sartorius) or 2-planetary centrifuge (Dual Axis Centrifugal or vortex mixer), can be used if it is ensured by correlation checks that with the settings and methods used an equivalent dispersion.
• the colorimetric evaluation is based on the following standards:
• the mixture was heated to 90 ° C and then 97 kg of 25 wt.% Nitric acid were added within 60 minutes. The reaction was carried out until the pH reached ⁇ 2.0. 8 hours were needed for this.
• the hematite seed suspension obtained was then cooled to ambient temperature and filled into a container. The required amount of hematite-germ concentration was then removed after complete stirring of the germ in the container and used for a Penniman structure.
• the hematite-germ concentration (as Fe 2 O 3 ) was 130 g / l.
• the mixture was mixed throughout the reaction time with a stirrer (80 rpm, 2, 1 m / s, inclined blade, 50 cm diameter, the power input was 0.31 kW / m 3 batch volume).
• a stirrer 80 rpm, 2, 1 m / s, inclined blade, 50 cm diameter
• the power input was 0.31 kW / m 3 batch volume.
• 161 liters of hematite-seed suspension having a concentration of 130 g / l (based on Fe 2 O 3) were added and the mixture was heated to 85 ° C.
• the gassing was started with 800 l / h of air.
• 2 m 3 / h of nitrogen was introduced via a gassing ring to maintain the reaction pH in the range of 2.2-2.4 (injection of nitrogen at pH 2.2 and shutdown at pH 2.4).
• the reaction mixture with iron (II) sulfate was added (29 liters with 206 g / l FeSO 4) and then filtered through a filter press and the resulting hematite pigment with deionized water to a conductivity of the filtrate of ⁇ 1000 Washed ⁇ 3 / ⁇ .
• the hematite pigment is subsequently dried at 80 ° C. to a residual moisture content of less than 5% by weight. Subsequently, the dried filter cake is crushed mechanically with a shredder. The hematite pigment was thus obtained in powder form in a yield of 81.0 kg.
• the reaction time was 185 h in total.
• the color analysis was carried out according to the method description described above.
• the chloride content in the dried pigment was determined to be 0.006 wt%.
• the viscosities in the paste viscosity test were: 0.358 Pa »s (at 500 / s), 0,341 Pa-s (at 1000 / s), 0.337 Pa-s (at 1500 / s) and 0,344 Pa-s (at 2000 / s) , Example 2 (comparative example)
• deionized water and iron (II) nitrate are added in the amounts so that a volume of 510 liters was reached and the concentration of iron (II) nitrate (calculated as anhydrous iron nitrate) was 62 g / l.
• the mixture was mixed throughout the reaction time with a stirrer (80 rpm, 2, 1 m / s, inclined blade, 50 cm diameter, the power input was 0.31 kW / m 3 batch volume).
• the reaction mixture was mixed with iron (II) sulfate (29 liters with 206 g / l FeSO 4) and then filtered through a filter press and the resulting hematite pigment with deionized water to a conductivity of the filtrate of ⁇ 1000 Washed ⁇ 3 / ⁇ .
• the hematite pigment is subsequently dried at 80 ° C. to a residual moisture content of less than 5% by weight. Subsequently, the dried filter cake is crushed mechanically with a shredder.
• the hematite pigment was thus obtained in powder form in a yield of 76.0 kg.
• the reaction time was 96 h in total.
• an a * value in the pulse of 29.5 CIELAB units and in the lightening an a * of 25.1 CIELAB units was measured. The sum of the a * values is therefore 54.6 CIELAB units.
• the paint test was carried out according to the method description described above.
• the iron oxide red pigments used according to the invention additionally have an increased grinding stability when they are prepared in the form of aqueous pigment concentrates with subsequent coating with an aqueous acrylate dispersion.
• the pigment concentrates were subsequently dissolved in an aqueous acrylate binder.
• the pigment concentrates prepared in this way were then mixed with a white binder in the form of a primer and stored for 24 h. Thereafter, the whitening lacquer was applied to white cardboard with a layer thickness of 200 ⁇ . After 24 hours the color was measured with a Datacolor SF 600 spectral colorimeter. The color differences were determined in accordance with DIN EN ISO 1 1664-4 (201 1-07) and DIN 5033 Part 7.
• the grinding stability is determined from the determined total color difference dEab * of the whitening lacquer prepared after 10 minutes of high speed dissolver dispersion Dispermat FM 10 SIP as a reference and of the whitening lacquer with the RM 500 color mixer after 30 minutes as a sample. Production of the pigment concentrates
• the aqueous pigment concentrate containing the pigment of Example 1 was prepared with a pigment concentration of 67%.
• the pigment preparation was given in a suitable container corresponding to the size of the batch and homogenized in the manner known to those skilled in the art.
• the pH is adjusted to 8.5 ⁇ 0.2 in the manner known to the person skilled in the art by addition of sodium hydroxide solution, 10% strength.
• the pigment concentrate used for the measurement has the following composition in% by weight:
• Dispex Ultra PX 4575 acrylate-based block copolymer from BASF SE
• Deuteron VT 819 Anionic heteropolysaccharide (xanthan gum) from the company
• Preventol D7 Formulation with isothiazolinones, LANXESS Deutschland GmbH Varnish binder
• aqueous acrylate dispersion from Alberdingk Boley GmbH, Germany, Alberdingk® AC 2025 was used as a lacquer binder. Preparation of white paste for whitening
• the titanium dioxide whitening paste for whitening was prepared with a pigment concentration of 70%.
• the pigment preparation was given in a suitable container corresponding to the size of the batch and homogenized in the manner known to those skilled in the art.
• the pH is adjusted to 8.5 +/- 0.2 in the manner known to the person skilled in the art by addition of sodium hydroxide solution, 10%, and dispersed for 15 minutes on the High Speed Dispermat Dispermat FM 10 SIP from Getzmann at 3000 rpm ,
• the white paste used for the measurement has the following composition in% by weight:
• Deuteron VT 819 Anionic heteropolysaccharide (xanthan gum) from the company
• Preventol D7 formulation with isothiazolinones, LANXESS Deutschland GmbH
• Sachtleben R-KB-2 micronised titanium dioxide (rutile) from Sachtleben Pigment
• the pigment concentrates thus prepared, the topcoat binder and the whitening paste for whitening were mixed in the following proportions and homogenized for 20 minutes in the color mixing device FAS 500 from Lau.
• the colorimetric evaluation is based on the following standards:
• Table 2 shows the total color difference dEab * in the paint test in the lightening with different hematite pigment from Example 1: titanium dioxide ratios.
• the iron oxide red pigments used according to the invention have a total color difference dEab * in the ratio pigment from Example 1 to Sachtleben R-KB-2 1: 1 of ⁇ 0.3, in the ratio 1: 5 of dEab * ⁇ 0.6 and im Ratio 1:10 of dEab * ⁇ 0.6.
• a total color separation dEab * for a pigment TiO 2 ratio of 1: 1 is less than 0.4.

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